In recent years, there have been proposed and developed various supercharged internal combustion engines capable of increasing an engine torque by supercharging intake air by means of a supercharging device installed in the intake system. One such supercharged engine has been disclosed in Japanese Patent Provisional Publication No. 2-119641 (hereinafter is referred to as “JP02-119641”).
The supercharged engine of JP02-119641 also employs a variable phase control mechanism (a VTC mechanism) configured to variably control a phase of valve open timing and valve closure timing of an engine valve (either one of intake and exhaust valves), and a controller configured to control the operation of the VTC mechanism depending on engine operating conditions, such as engine load and/or engine speed. For instance, during high load operation, a valve overlap of intake and exhaust valves is controlled to become greater (longer). Conversely during low load operation, the valve overlap is controlled to become smaller (shorter).
Furthermore, when an engine load rise has occurred from a non-load state (e.g., an idling state where the engine runs without load with an accelerator pedal released) or a light engine load state, the controller, incorporated in the supercharged engine of JP02-119641, is configured to execute valve-overlap enlargement control in such a manner as to increase residual gas in the engine cylinder, thus reducing exhaust emissions, such as oxides of nitrogen (NOx).